Figure 6. Rats experience helping rats of a familiar strain as rewarding.
(A) The latency to door-opening decreased along the days of testing for rats tested with familiar strains (open circles) but not for those tested with unfamiliar strains (filled squares). (B) The proportion of openings that were followed by a repeated opening on the next day of testing was higher for trapped rats from familiar strains (left of dashed line) than from unfamiliar strains (right of dashed line). (C) Opening data from representative rats of each condition are illustrated. Fostered SD rats were tested for 13 days.